The present invention relates to a method of calibration of a system which operates in dependence on a sensor in a motor vehicle.
In a motor vehicle a great number of sensors are provided, for example path sensors, angle sensors, speed sensors, acceleration sensors, pressure sensors, power sensors, etc. These and other sensors are required to provide an optimal control of the components of a motor vehicle, such as the motor, the braking device, the transmission etc., in correspondence with the commands of the driver and the existing conditions.
For an optimal control it is necessary to guarantee that the sensors detect, as accurate as possible, the variables to be detected, with the consideration of what kind of control is performed.
Since all sensors have certain tolerances and/or the results supplied by the sensors often depend not only on the variables to be detected but also on their age and/or application conditions, for example their arrangement, their operational voltage, the degree of dirtying, etc., measures must be taken to eliminate the influences of the above mentioned factors on the results supplied by the sensors.
In accordance with one of these measures, the system which contains the sensors is calibrated during the manufacture and also after mounting in the motor vehicle. However, it can not be guaranteed, in particular for all systems, that they will operate over long times with sufficient accuracy.
In addition, or alternatively to this approach, it is also proposed to construct the sensors so that the occurring offset (zero point displacements) can be compensated automatically in the sensors. Such a sensor is disclosed for example in the German patent document DE 197 53 975. However, not all sensors can be constructed in this way. Moreover, only those offsets can be compensated, whose occurrence has certain causes. It is for example not possible to compensate an offset which is caused by the fact that the sensor is not built-in exactly before the use.
A further possibility for recognition and elimination of the above mentioned affect is that, the variables detected by sensors can be detected by several, differently operating sensors. This however requires high technical and financial expenses.
For the above mentioned reasons, it is a conventional practice to provide in the systems which operate depending on the sensors, a post calibrations within greater or smaller time periods. This can be provided for example during regular maintenance works in the motor vehicle.
However, it is not sufficient for all systems. Some systems must be post-calibrated in shorter time intervals.
This can be achieved for example in that the owner or the driver calibrates the respective systems in accordance with a predetermined specification. This can be also performed substantially automatically so that the owner or the driver must perform himself few simple actions, without extensive knowledge by the owner or the driver.
Accordingly, it is an object of the present invention to provide method of calibrating of a system which operates depending on a sensor in a motor vehicle, which makes possible, in a simple manner and without participation of the owner or the driver of the vehicle, to guarantee that the system which depends in its operation on the sensors always operates in an orderly fashion.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a method of calibration of a system which operates depending on a sensor, which includes the steps of first testing, with the use of sensors available in a motor vehicle or with the use of data representative of selected conditions or processes or signals of control devices available in the motor vehicle, whether it can be ascertained that nobody is located in a motor vehicle which can influence variables to be determined by a sensor of a system to be calibrated; and performing the calibration when the testing confirms that it can be ascertained that nobody is located in the motor vehicle which can influence variables to be detected by the sensor of the system to be calibrated.
Then it is ensured that nobody in the motor vehicle is located which can influence the variables detected by the sensor to be calibrated and/or endangered or distorted by a calibration, or in other words for example when nothing is located in the vehicle, the variables to be detected by the sensors to be calibrated have definite values or can be adjusted so that they have definite values. When these values are compared with the results supplied by the sensors, then it is possible to determine whether and sometimes in what range the value supplied by the sensor deviates from the actual value. This difference can be stored in a non-volatile memory, such as for example EEPROM or utilized for correction of the values supplied by the sensor.
When something is located in the vehicle, which has influence on the variables to be detected by the sensor to be calibrated or can apply such influence, or is endangered or distorted by the calibration, it can be verified without or with insignificant expense. For this purpose, however individual available informations must be evaluated. These informations includes for example the following informations:
whether the motor is running;
whether the ignition key is inserted,
whether the vehicle doors are closed (determinable by the door switches for the inner illumination)
whether the doors are locked (determinable by the door lock contacts of the central locking), and/or
whether somebody is located in the vehicle (determinable by the inner space monitoring through an alarm device and/or by the seat occupying recognition for the air bag control).
Thereby it is possible in an exceptionally simple manner that the senses available in the vehicle can be automatically post-calibrated arbitrarily often and without cooperation of the owner or driver of the motor vehicle.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.